Local aspects of the adsorbate-substrate chemical bond in N/Cu(100) and O/Cu(100)

Both the occupied and unoccupied adsorbate valence states have been probed by x-ray emission and x-ray absorption spectroscopies for N/Cu(100) and the low coverage phase of O/Cu(100). By carrying out experiments using two different measurement geometries, the adsorbate out-of-plane states ${(2p}_z)$ have been separated from the in-plane states ${(2p}_{\mathrm{xy}}).\mathrm{}$ The experimental results are compared to the partial density of states (DOS) obtained from full-potential linear muffin-tin orbital calculations, with good agreement in the case of N/Cu(100). This agreement confirms that it is possible to interpret the experimental data in terms of the adsorbate partial DOS. Our combined experimental and theoretical study also provides a detailed understanding of the local chemical bond for N and O adsorbed on Cu(100).